1. Field of the Invention
The present invention relates, in general, to high efficiency modular OLF (oblique louver fin) heat exchangers preferably used as condenser, evaporator and radiators of automobiles or military tanks or the like and, more particularly, to a high efficiency modular OLF heat exchanger having newly designed louver fins provided with oblique strips, the oblique strips being capable of forming transverse and longitudinal vortexes in a main gas flow around each louver fin while breaking the boundary layer of the gas flow, thus enhancing the heat transferring effect of said fins.
2. Description of the Prior Art
As well known to those skilled in the art, the thermal resistance, caused by external gas or atmospheric air, in conventional plate-fin heat exchangers is higher than 80% of the total thermal resistance of such a heat exchanger, so that the heat exchanging effect of such heat exchangers is almost completely determined by the operational function or heat transferring effect of fins set in said heat exchangers.
The fins of such heat exchangers typically have a small hydraulic diameter and a low gas density within a flow region of low Reynolds number, so that it is possible to somewhat improve the heat transferring effect of the fins by changing the geometrical configuration of said fins within the small Reynolds number flow region. Such a change in the geometrical configuration of said fins preferably reduces the thermal resistance of the fins, resulting in an improvement in the heat transferring effect of the fins.
In the prior art, louver fins and offset strip fins (OSF) have been typically used as fins for such heat exchangers.
It is noted that the louver fins have a high thermal efficiency. However, the typical louver fins are problematic in that the thermal efficiency of the fins is undesirably reduced at positions around the rear strips of each fin. That is, since a gas flow is formed along the louver angle at positions around the front strips of each fin, the path length of the gas flow around the front strips is lengthened. This allows the heat transferring effect of the fins at positions around the front strips to be improved. However, since the path length of the gas flow at positions around the rear strips of each fin is shortened, the heat transferring effect of the fin at positions around the rear strips is regrettably reduced. In addition, the strips of the typical louver fin are designed to have an angle of attack of 90.degree. with respect to the gas flow. Therefore, the strips do not form any swirl in the gas flow, so that the strips fail to give good heat transfer enhancing effect, caused by a longitudinal vortex, to the louver fin.
On the other hand, the typical offset strip fins (OSF) are designed to be offset with each other, thus preferably breaking the boundary layer of the gas flow due to a primary offset effect. However, the typical offset strip fins are problematic in that they fail to form any swirl in a gas flow, thus merely providing a one-dimensional or unidirectional offset effect along the main gas flow on the path line. Therefore, the heat transferring effect of the offset strip fins is regrettably lower than that of the above-mentioned louver fins.
Another problem, experienced in the heat exchangers having the above-mentioned louver or offset strip fins, is that the fin assembly is not formed as a module, so that it is almost impossible to manufacture heat exchangers while changing the size and capacity of the heat exchangers when necessary.